1. Field of the Invention
This invention relates to a film guide mechanism for use in a camera in which film is delivered through the film-cartridge delivery port by rotating the spool shaft of the film cartridge.
2. Related Background Art
FIG. 3 is a perspective view of a camera in which a conventional film cartridge model 135 can be loaded. In FIG. 3, a film cartridge 10 has a cylindrical portion 11 and a delivery portion 12. Within the cylindrical portion 11, film FI is housed in a wound state, and the leading edge thereof has been drawn out from the delivery portion 12 beforehand. In a camera main body 1, a film cartridge chamber CC, in which the above film cartridge 10 is loaded, is formed on one end side, and a spool chamber (not shown), in which a film take-up spool is housed, is provided on the other end side. An aperture AP is provided between the film cartridge chamber CC and the spool chamber.
Numerals 2a and 2b are inner rails for positioning the film FI, and control members 3a and 3b control the movement of the film FI in the width direction. A curved surface is formed on an angular area between the wall of the film cartridge chamber CC on the aperture side and a plane 4 in which the aperture AP has been formed. Curved surfaces are also formed on the angular areas of the inner rails 2a and 2b on the film cartridge chamber side as shown in FIG. 4 in order to prevent film to be delivered from being damaged by the angular areas.
The film cartridge 10 is loaded in the film cartridge chamber CC with the film FI drawn out as shown in FIG. 3. When the back cover (not shown) is closed after the leading edge of the film FI is wound around the film take-up spool, the film is held in a film passage between a pressure plate fitted to the back cover and the above film rails 2a and 2b to keep the film FI in a plane state by the pressure plate. When the film take-up spool is rotated in this state, the film FI is wound.
In, for example, U.S. Pat. Nos. 4,832,275 and 4,834,306, such a film cartridge 20 as shown in FIG. 4 is disclosed. The film cartridge 20 has a cylindrical portion 21 and a delivery portion 22 which is projected in the tangential direction thereof. At the tip end of the delivery portion 22, a film delivery port 22a is provided, and a spool shaft 21a is rotatably supported within the cylindrical portion 21. The film FI is housed while it is wound around this spool shaft 21a, and the leading edge of the film FI is located within the film cartridge 20 before the film cartridge 20 is loaded in the camera. In other words, the leading edge of the film FI is not drawn out from the delivery portion 22, unlike the above film cartridge 10. The delivery poriton 22 is provided with light shielding members 23a and 23b.
When such a constituted film cartridge 20 is loaded in the above-mentioned film cartridge chamber CC of a camera main body 1 as shown in FIG. 1, the spool shaft 21a is connected with the film delivery mechanism on the camera main body 1 side, which rotates the spool shaft 21a clockwise in FIG. 1. This drives the film FI to deliver its leading edge outward from the delivery port 22a through between the light shielding members 23a and 23b. The delivered film FI passes along the film passage between the above-mentioned pressure plate of back cover and the film rails 2a and 2b and is guided into the film take-up spool (not shown).
Such a film cartridge 20 will be called "thrust film cartridge" in this specification.
This thrust film cartridge 20 has an advantage that it can be simply loaded in a camera main body. Since, however, the leading edge of the film FI is not drawn out from the film cartridge, the following problems occur when it is loaded in the above-mentioned conventional camera.
That is, the leading edge of the film FI is curled as shown in FIG. 4 even after it has been delivered from the film cartridge 20 because of a peculiarity of winding when the film was wound around the spool shaft 21a within the film cartridge 20. For this reason, the leading edge of the film FI is likely to drop as shown in FIG. 4 by abutting on the curved surface of the inner rails 2a and 2b, and not to be guided into the film passage, making it impossible to deliver the film FI.
Also when delivering of the film is continued in this state, the film is jammed within the film cartridge 20, and will be useless. Such a problem easily occurs especially when the light shielding member 23a has been manufactured longer than 23b owing to size variations during manufacture. Further under a special circumstance, the film FI may curl in the opposite direction to the above as shown in alternate long and two short dashes line, and the same problem as mentioned above occurs in this case.
With regard to the film width direction, on the other hand, when the film cartridge 20 is placed on the bias against the control members 3a and 3b as shown in FIG. 5, the film is likely to strike the control member 3a (or 3b), making it impossible to deliver the film or making it useless in the same way as mentioned above.